将一个对象传递给多个 IServiceCollection 扩展

Question

我需要将一个对象传递给我创建的几个IServiceCollection 扩展，并且我的所有扩展方法都使用该对象并注册它们相关的依赖项。下面是我的代码的样子：

程序.cs

var myObject = new MyObject(); //MyObject implements IMyObject
var builder = WebApplication.CreateBuilder(args);
builder.Services
       .AddMyExtension1(myObject)
       .AddMyExtension2(myObject)
       .AddMyExtension3(myObject)
       ...
       .AddMyExtensionN(myObject);

var app = builder.Build();
...
app.Run();

示例扩展：

public static class MyExtensions{

  public static IServiceCollection AddMyExtension1(
        this IServiceCollection services,
        IMyObject myObject)
  {
     //do something
     //register some dependencies
     return services;
  }
}

我知道使用BuildServiceProvider 可能会导致代码异味/“导致创建单例服务的额外副本”。谁能推荐一种更好的方法来在我的扩展方法中使用 myObject 实例，而不是在我的所有方法中将其作为参数传递？

Answer 1

如果没有看到myObject 的实际用法，很难争论什么是最好的方法。如果所有自定义 AddMyExtension.. 方法都需要它，则可能应该在运行时注入和解析以进行相应的注册。

如果在您的情况下不可能或只是个坏主意，您可以创建一个新接口，其实现基本上是 IServiceCollection 的包装器，并将其用于注册。像这样的东西：

public interface IMyServiceCollection : IServiceCollection
{
    public IMyObject MyObject { get; }
}

class MyServiceCollection : IMyServiceCollection
{
    private readonly IServiceCollection _serviceCollection;

    public IMyObject MyObject { get; }

    public MyServiceCollection(IServiceCollection serviceCollection, IMyObject myObject)
    {
        _serviceCollection = serviceCollection;
        MyObject = myObject;
    }

    public IEnumerator<ServiceDescriptor> GetEnumerator() => _serviceCollection.GetEnumerator();

    IEnumerator IEnumerable.GetEnumerator() => ((IEnumerable)_serviceCollection).GetEnumerator();

    public void Add(ServiceDescriptor item) => _serviceCollection.Add(item);

    public void Clear() => _serviceCollection.Clear();

    public bool Contains(ServiceDescriptor item) => _serviceCollection.Contains(item);

    public void CopyTo(ServiceDescriptor[] array, int arrayIndex) => _serviceCollection.CopyTo(array, arrayIndex);

    // the rest of IServiceCollection delegating implementation ...
}

扩展：

public static class ServicesExts
{  
    public static IMyServiceCollection WithMyObject(this IServiceCollection services, IMyObject obj) => new MyServiceCollection(services, obj);
}

然后让所有AddMyExtension... 方法接受并返回IMyServiceCollection，调用更改为：

builder.Services
    .WithMyObject(myObject)
    .AddMyExtension1()
    .AddMyExtension2()
    ...
    .AddMyExtensionN();

或具有值元组的类似方法：

public static class ServicesExts
{  
    public static (IServiceCollection Collection, IMyObject Object) WithMyObject(this IServiceCollection services, IMyObject obj) 
        => (services, obj);
}

而AddMyExtension... 有点像：

public static (IServiceCollection Collection, object Object) AddMyExtension(this (IServiceCollection Collection, object Object) tuple)
{
     // do the registrations ...
     return tuple;
}

用法看起来一样。